- Drug refractory (including beta-blockers and one anti- arrhythmic or has documented intolerance to or toxicity from beta-blockers and at least one anti-arrhythmic) ventricular tachy-arrhythmias leading to an ICD shock after at least one catheter ablation procedure for VT, OR drug refractory ventricular tachy-arrhythmias leading to an ICD shock that are not amenable to or clinically appropriate for catheter ablation procedures. Clinically appropriate is defined as those patients with MMVT. Those with PMVT or idiopathic VF are not required to have had previous ablation. ICD shock needs to have occurred in the 6 months prior to randomization.